CIPRIAN ANDREI OBER - USAMV Cluj · ciprian andrei ober . summary of the phd thesis . observations regarding the usage of the polypropylene prosthetic biomaterials in abdominal wall

Observaţii privind utilizarea biomaterialelor protetice din polipropilenă 2011 în defecte parietale abdominale la animale

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UNIVERSITATEA DE ŞTIINŢE AGRICOLE ŞI MEDICINĂ VETERINARĂ CLUJ NAPOCA

ŞCOALA DOCTORALĂ FACULTATEA DE MEDICINĂ VETERINARĂ

CIPRIAN ANDREI OBER

SUMMARY OF THE PhD THESIS

OBSERVATIONS REGARDING THE USAGE OF THE POLYPROPYLENE PROSTHETIC BIOMATERIALS IN ABDOMINAL

WALL DEFECTS IN ANIMALS

CONDUCĂTORI ŞTIINŢIFICI

Prof. Dr. Liviu OANA

Prof. Dr. Cornel CĂTOI

CLUJ-NAPOCA

2011


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The thesis, entitled "Observations regarding the usage of the polypropylene prosthetic biomaterials in abdominal wall defects in animals" is fully justified, both from the scientific point of view and practical, primarily because it solves the problem of frustrated recurrences occurring frequently as a result of simple raffia of abdominal breaches, and that the application of a prosthetic biomaterial ensures an increased resistance of the abdominal region repaired. Frequent recurrences occurred after disruption of suture material, after a simple raffia technique or after their sectionning of the edges of the abdominal wall, often fibrosed, has to the study of this subject.

Worldwide, in human medicine and most recently, also in veterinary medicine, there are a multitude of prosthetic biomaterials (absorbable/nonabsorbable, mono/multifilamentous, micro/ macroporous) and a series of procedures of abdominal breaches prosthetic repairing, although a "prosthetic ideal biomaterial " or an "ideal technique of implantation” are still unknown. Clinical patients alone can not provide sufficient data to lead to an accurate assessment of biocompatibility of such biomaterials, that is why this thesis research had the following general objectives:

• Evaluation of two operatory techniques of implantation of prosthetic polypropylene meshes in the repair of abdominal wall defects in animals.

• Evaluation of clinical changes and postoperative complications.

• Monitoring of some blood parameters, relevant for appreciating the general and local biocompatibility of prosthetic meshes (basic filament of polypropylene).

• Highlighting local tisular changes - macroscopic and microscopic – induced by prosthetic meshes in a rabbit model, at defined post-operative intervals.

Content of the thesis

The thesis is structured in two principal parts: the first part includes an introduction and data from literature and the second part includes personal research, with objectives, materials and methods, experimental protocol, results and discussion, conclusions and bibliography.

The first part includes 4 chapters (2-5). • Chapter 2 presents anatomical data concerning the abdominal wall in animals. • Chapter 3 approach defects and parietal abdominal pathological processes which can be managed by prosthetic repair, in animals. • Chapter 4 presents an exhaustive and chronological approach of types of prosthetic meshes that existit on the market. • Chapter 5 presents the main surgical techniques of implantation of prosthetic meshes.

The section of personal researches includes four studies, divided into four chapters:

biocompatibility of prosthetic meshes in horses, biocompatibility of prosthetic meshes in dogs, biocompatibility of prosthetic meshes in other species and biocompatibility of prosthetic meshes in rabbits – experimental study.


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Objectives of the paper

The aim of this paper was to determine the biocompatibility of prosthetic mesh of

polypropylene applied to repair the abdominal wall defects in clinic patients, by evaluating the efficiency of two different techniques of implantation, by evaluating the postoperative discomfort induced by the mesh and by monitoring some relevant blood parameters.

Observation of integration into host tissue of the prosthetic mesh was made by observing, in dynamic, the local tissular behavior of the mesh (histological exams), in an experimental rabbit model.

Corroborating data from the clinical patients with the experimental model, could lead to an accurate appreciation of the in vivo behavior of a prosthetic biomaterial, designed to repair this pathology with high incidence in animals - abdominal wall defects.

BIOCOMPATIBILITY OF PROSTHETIC MESHES IN HORSES

Aim of the study

This study’s purpose is the evaluation of two implantation techniques of prosthetic meshes in abdominal wall defects in horses, evaluation of the clinical changes and postoperative complications, highlighting host tissue changes induced by local prosthetic meshes and monitoring some blood parameters, relevant for the appreciation of local and general biocompatibility of prosthetic meshes.

Material and method Clinical patients were represented by 15 horses of different race, age, sex and services,

private property, casuistry presented for diagnosis and treatment during 2005-2011. These patients had different deffects of the abdominal wall (eventrations, inguinal hernias, eviscerations), the causes of these deffects being either traumatic, either as a result of sustained efforts or postoperative dehiscence.

The choice of the anesthetic protocol was based on the preoperative biological findings, on the size and localization of the defect and also depending on the existent equipment and economical considerations. In this context, we used two anesthesia protocols, TIVA (total intravenous anesthesia) protocol and PIVA (partially intravenous anesthesia) protocol. Clinical monitoring was done using the major semiological methods and by the use of the Midray PM-9000Vet multiparameter, assesing the heart rate, respiratory frequency, respiratory volume, temperature, capilary refill time, presence of the palpebral reflex and movements of the eye, SpO2, arterial blood pressure - measured noninvasively -, ETCO2, ECG.

The meshes used in the study contain synthetic polypropylene (D-tek, Polypropylene Mesh) nets (Fig. 1) and are commercially available in 15 X 15 cm and 30 X 30 cm sizes. The 15 X 15 cm meshes are packed extended, the 30 X 30 cm are packed folded. Each mesh shows a label that contains the data needed in preparing the surgical protocol. The meshes are nonabsorbable, their special texture giving porosity to the mesh, these polypropylene meshes are part of the macroporous category. Being a biomaterial resistant to stretching and tearing, it can be cut in any form, without damaging or unwinding.

Prosthetic meshes are packed sterile and can be resterilized by ethylene oxide. In order to not induce additional reactions to another type of material, for the fixation of the


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meshes we used suture material with the same composition, polypropylene filaments (D-tek polypropylene, PM). This is a suture material packed sterile, nonsorbable, synthetic (Fig. 2) and monofilamentous. It is a stereoisomer of polypropylene (crystalline form, linear polyolefin). The D-tek PM suture material is available in sizes from 10 / 0 to 1, colored blue to increase visibility when used.

Fig.1. Mesh used in study Fig. 2. Wires used Prosthetic meshes implantation techniques used were the subcutaneous premuscular-

aponevrosis technique (epifascial or onlay) (Fig. 3) and the retromuscular technique (preperitoneal or sublay (Fig. 4). The election of the implantation method has was influenced by the age of the patient, the biological status, the size and the amount of time that past since the abdominal wall defect was produced.

Fig. 3. Epifascial technique Fig. 4. Retromuscular technique

In the cases of inguinal hernias, after the incision of the hernial sac over the superficial inguinal ring, with revealing the hernial contents, spermatic cord and testicle, after repositioning of the intenstine and exteriorising the testicle, we made a transfixing ligature of the spermatic cord with resorbable suture material (poliglicolic acid). After testicle ablation, in both patients, we placed the prosthetic meshes using the epifascial tehnique, on the superficial inguinal ring level. We recommend the technique that includes orchidectomy because it provides a better closure of the inguinal ring. We do not recommend keeping the testicles, exception being the high biological value patients and in the case of traumatic hernias; maintaining the testicle involves increased risks and high incidence of postoperative complications.

Postoperative, the patients were housed in individual hygienic boxes. Food was a light one, based on concentrates, to avoid overfeedings, brutish feed being introduced progressively, after 2-3 weeks.


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Patients with inapetence have been treated with Ringer solution and 10% Glucose

perfusion, for 3 days postoperative. Overstressing has been avoided, efforts intensity being increased gradually. Housing in

individual boxes, with the light feeding ration based on concentrates and pellets and limiting the movement walks to once a day, have provided proper healing of the repaired region in the patients from our study.

Postoperative, all patients were monitored, taking into account their general status (apetite, temperature, heart rate, respiratory frequency, colic signs) and the evolution of the local processes (seromas, haematomas, infections, recurrences) and healing.

Results Postoperative all patients showed some depression and decreased appetite, abdominal

discomfort, revealed by tachycardia, tahipnea and signs of colic (autoascultation, frequent changing of position, striking the ground with the hoof, recumbency). These signs have persisted during the first 48-72 h, during which time the patients were carefully monitored and treated with antibiotics and anti-inflammatories. Also, throughout this period of time, compared to preoperative values, the major functions were elevated.

Prosthetic meshes did not induce toxic phenomena, manifested by piloerections or behavioral disorders.

Local macroscopic changes observed in the first 14 days postoperative were represented by 13 seromas, a hematoma, a local infection and a reccurence (Table 1). Daily drainage and rubefactions with iodine tincture from two to two days have provided a gradual release of seromas at the level of the suture.

Table 1 Macroscopic local abnormal findings seen in first 14 days after implantation

Local abnormalities

First week postoperative Second week postoperative

Seromas

11 2

Hematomas

1 -

Local infections

- 1

Reccurence - 1

After the progressive release of the seromas, at the level of the drainage contraincisions, to prevent infections we have introduced oxytetracycline spark-plugs. The hematoma was fully resorbed after rubefactions.

In one patient, with breaking of the abdominal wall caudally to the tumefaction, a reccurence occured. The abdominal wall suffered a dehiscence in the caudal third with intestine engaging at this level, that clinically generated the aspect of a large reccurence. The suture material on the caudaly side of the breach sectioned the weak muscular tissue, post caesarean. This reccurence did not determine clinical signs or general status alteration, so the decision was made to postpone a new surgical intervention until the resistance restoration through fibrosis of the abdominal wall, that would allow implanting and mantaining a new prosthetic biomaterial.


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In one patient an infection of the implanted mesh locus occured. General condition worsened progressively, and with the consent of the owner, the mare was euthanisied two weeks postoperative.

On postmortem macroscopic examination it has been observed that around the mesh a pyogranuloma with an intense proliferation of granulation tissue, highly vascularized was formed. Intense vascularization attested early angiogenesis phenomena. Striated muscular tissue from the mesh-host interface tissue contained inflammatory infiltrations with neutrophils and macrophages with ceroids. In the abdominal muscle tissue we have observed massive fibrosis phenomena, with of muscle fibers atrophy. Overall, two weeks after the surgery, at the locus of implanted mesh, there was a chronic active inflammatory reaction with macrophages with ceroids and hemosiderin in the highly fibrosed connective tissue and neutrophils due to sepsis.

In order to assess local and general biocompatibility of prosthetic polypropylene meshes, at defined postoperative time intervals, we monitored biochemical and immunological parameters that reflect the biocompatibility. Tests were conducted at the laboratory of medical veterinary analysis ERI VET from Cluj-Napoca. Complete haemoleucograms with blood elements, C reactive protein, serum total proteins, albumin and fibrinogen, from biochemical indices, were monitored. IgE was the immunologic parameter that was evaluated.

In terms of haemoleucogram, an increas of the total number of white elements, neutrophilia were observed, maximum values being recorded in the first days postoperative. These increased values are due to tissue aggression induced by the surgical act and prosthetic mesh, with maximum aggression in the early postoperative days, intensity decreasing with the beggining of reparatory activity.

Further increasing of monocyte count, certified the beggining of local reparatory activity. Significantly increase of blood fibrinogen values in the first week postoperative, compared to the preoperative values, confirmed the presence of an acute systemic inflammatory process. This is also confirmed by the significant increase of postoperative C reactive protein values.

A slight hyperproteinemia, but without significant increase, was observed the 3rd day postoperative, probably due to the increased fibrinogen and C reactive protein; in the following 14 days, values of total protein were in physiological limits.

Classified as negative protein of acute phase, we observed a hypoalbuminemia in the first 2 days postoperative, and then the maintainance of constant values of serum albumin after the implantation of the prosthetic meshe.

Although we observed a slight increase of immunoglobulin E, that was clinically insignificant, in the first days postoperative, there was no allergic type phenomena or hypersensitisation in any patient.

The subcutaneous premuscular-aponevrosis procedure was more easy to apply, but it predisposed to the formation of seromas, hematomas and infections by the large spaces created during dilacerations. Retromuscular procedures were more laborious, require experience, but provided a better fixation of the biomaterial in host tissues, providing increased resistance of the abdominal wall repaired and protection of the mesh from possible infections.

Our results permit us to recommend the use of prosthetic polypropylene meshes for the repair of the abdominal wall defects in horses, without trying closure of the defects by a simple raffia.


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BIOCOMPATIBILITY OF PROSTHETIC MESHES IN DOGS Aim of the study The purpose of the study was the evaluation of two prosthetic mesh implantation techniques in defects of the abdominal wall in dogs, clinical observation of changes and postoperative complications, highlighting the local tissue changes induced by prosthetic meshes and monitoring of some blood indices relevant for the assessment of local and general biocompatibility. Material and method

Clinical patients were represented by 33 dogs, of different race, age, sex and services, private property, casuistry presented for diagnosis and treatment during 2005-2011 These patients had different deffects of the abdominal wall (eventrations, inguinal hernias), the causes of these deffects being traumatic.

For the purpose of enabling the accomlishment of prosthetic mesh implantation techniques, the most suitable anestetic protocols were used. Xylazine or midazolam were used for premedication, ketamine, propofol or thiopental were used for induction. All the patients were intubated using adequate endo-tracheal tubes. For mantainance of the anesthesia we used sevofluran or isofluran, combined with oxigen-air compound, respectivey 100 % oxigen. The anesthetic machines used were Drager Cato (for the use of sevofluran) and Midmark MatrxTM VME2® (for the use of isofluran). Intraoperatory analgesia was obtained by administrating tramadol.

Clinical monitoring was done using the major semiological methods and by the use of the Midray PM-9000Vet multiparameter, assesing the heart rate, respiratory frequency, respiratory volume, temperature, capilary refill time, presence of the palpebral reflex and movements of the eye, SpO2, arterial blood pressure, measured noninvasively, ETCO2, ECG.

Meshes used in the study were the same as those used in the case of horses, 15X15 cm dimensions.

The prosthetic meshes implantation techniques were the subcutaneous premuscular-aponevrosis method (epifascial or onlay) (Fig. 5) and the retromuscular method (preperitoneal or sublay) (Fig. 6). The choise of the implantation procedure took into consideration, as in the case of horses, the age of the patient, the biological status, the size and the time that has passed since the abdominal wall defect was produced. In the cases of perineal hernias, after the incisions of the skin and the subcutaneous connective tissue and the examination of the hernial contents, the prosthetic mesh was fixated on the external anal sphincter, internal obturator muscle, coccygeus muscle and levator ani muscle. Adipose retroperitoneal tissue was then sutured over the prosthetic mesh.


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Fig. 5. Epifascial fixation of the mesh

Fig. 6. Preperitoneal fixation of the mesh

Postoperative patients were housed in individual hygienic boxes. Food was a light one, based on semifluids, to avoid overloading of the digestive tractus. To avoid postoperative complications, food was administered mor often, in smaller quantities, introduced gradually, depending on the evolution of each patient. Patients with inapetence have been treated with Ringer solution and 5% glucose perfusion, 3 days postoperative.

If the case of perineal hernias the postoperative dietary regime is extremely important, it should avoid constipation, which requires great intra-abdominal efforts during defecation, thus the risc of recurrences and dehiscence. Preoperative protocol, using laxatives (Metamucil) was continued 2 weeks postoperative. To reduce tumefactions, cold compreses were also applied in the operated areas 2-3 times daily ( for 15-20 minutes) for 3 days postoperative. On the 7th and 14th day, mesh fixation and remediation efficiency were verified by postoperative rectal examinations.

Postoperative analgesia was obtained using butorphanol, intramuscularly, every 4 hours, the first day postoperative. After this interval, for the next 3 days, carprofen tablets were given per os, every 12 hours. Antibioticoterapy for 5-7 days post-operative consisted intramuscular administration of synulox.

Results

Postoperative, all patients had a mild state of depression and abdominal discomfort. These signs persisted the first 48 h, time during which the patients were carefully monitored and treated with antibiotics and analgesics.

In two of the patients with perineal hernia (patients 20 and 22), tenesmus persisted 3, respectively 5 days postoperative, then remitted.

Through the first days postoperative, compared to the preoperative period, the values of the major body functions were increased, but the magnitude of these changes was lower than that registered in horses. The increase of these values was due to the inflammatory process initiated by the evident tissue agression from the first days postoperative.

Local macroscopic changes observed in the first 14 days postoperative were represented by 12 seromas, 2 hematoamas, 2 local infections, and one hernial recurrence (Table 2).


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Table 2 Macroscopic local abnormal findings seen in first 14 days after implantation

Local abnormalities

First week postoperative Second week postoperative

Seromas

9 3

Hematomas

2 -

Local infections

2 -

Recurrences

1 -

Seromas were seen in pacients in which mesh fixation was done using the premusculo-aponevrotic subcutaneous tehnique, due to the fact that the subcutaneous dilacerations were wider. Their resorbtion was ensured through daily drainages and rubefactions with iodine tincture every two days.

Hematomas appeared in the case of 2 patients and were fully resorbed after 5 days, using rubefactions with iodine tincture, every second day.

In one patient a hernia recurrence occured. This happened due to the incorrect apliance of the alimentary diet and postoperative effort regime and had as consequence the bracking of the suture material fixing the prosthetic mesh, in the caudal part, that led to the engaging of the small intestine and epiploon in the hernial sac. Clinically, the pacient didn’t present any alteration of the clinical status, the great body functions being in fisiological ranges. The treatment was another surgical intervention, by opening the tumefaction, removing the mesh and applying epifascially another prosthetic mesh.

Macroscopical and microscopical evaluation of the implanted prosthetic mesh was accomplished in the case of one patient, three years after the implantation. The macroscopical exam of the perineal area showed the mesh and the suture material without structural defects. Both the mesh and the suture material, were integrated in a dens fibrous tissue, hard deteachable, that covered the entire mesh and the mesh-tissue interface. The microscopical exam of the tissue in the prosthetic area, showed good nature proliferative conjuctive fibrous tissue. This tissue contained paralel thin colagenous fibers, distributed in fascicles, that penetrate and occupy the prosthetic mesh, forming all together a comune, very resistent structure, without any areas of tissue laxity.

We monitored the same blood parameters as in the case of horses. In dogs, the increased total number of white elements, immediately postoperative, was not so evident as in horses, which makes us believe that, in this case, the surgical act and prosthetic mesh induced an aggression with smaller intensity. As in horses, the values decreased gradually with the repairing activity.

In the leukocyte formula presented, neutrophilia corresponding to aggression induced by the prosthetic biomaterial was seen in the first days postoperative, then the increase of the monocyte procentage.

Postoperative values of the C reactive protein and fibrinogen increase significantly in dogs, suggesting the existence of a systemic inflammatory process.

In dogs, we observed a significant increase of the total protein count on the 2nd and 3d days postoperative, compared with the preoperative values, then, from the 7th day, the values were back within fiziological ranges.


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Albumin values decreased slightly in the first and second postoperative days, after that being in the physiological ranges.

Although the level of immunoglobulin E has slightly increased in the first days postoperative, clinically we have not seen any allergic phenomena, hypersensitisation or rejection of implanted biomaterials.

The average duration of surgical procedures was 1.5 hours (between 1.2-2.1 h). With prosthetic repair of hernial rings orchidectomy was also performed. We recommend

mentaining the testicles only in valuable patients with reproductive value and only after serious disscutions with the owners concerning the complications that may arise if the testicles are maintained.

Subcutaneous premuscular-aponevrosis method easier to aply, but, also in dogs, it predisposed to seromas, hematomas and infections, due to the large spaces created during dilacerations. The retromuscular method assured a better and safer fixation in terms of muscular-fascial resistance generated in time. Neither in dogs can we apply a standard technique of implantation of prosthetic meshes, each particular case requiring an individual evaluation for choosing the best method.

Also in dogs, prosthetic aloplasty using polypropylene meshes has proven a safe and efficient solution in the management of the abdominal wall defects.

The results of our study allow us to recommend the use of prosthetic polypropylene mesh in the repair of abdominal walldefects, without attempting the repair by a simple raffia.

Biointegration of implants remedies and postoperative reparatory processes took place more rapidly compaired to what happens in human patients, so, the dog can be considered a very good model for the study and interpretation of results observed after prosthetic implants procedures.

BIOCOMPATIBILITY OF PROSTHETIC MESHES IN OTHER ANIMALS Aim of the study

The purpose of the study is to evaluate the procedure of subcutaneous premuscular-aponevrotic implantation of prosthetic polypropylene mesh in the case of parietal abdominal defects in ruminants and swine and apreciating the clinical modifications and postoperative complications.

Material and method

The clinical patients were represented by 3 bovines, 3 swine and a sheep, that presented

abdominal wall defects, casuistry presented for diagnosis and treatment during 2005-2011. These patients had different deffects of the abdominal wall (eventrations, umbilical hernias), the causes of these defects being traumatic or congenital.

In the case of the bovines with eventration the anesthetic protocol that cosisted of the xylazine-ketamine combination and sustained by a paralombar regional analgesia proved to be a good one. In the case of the calf, xylazine i.m. was used for premedication, and propofol i.v. for induction, maintaining the anesthesia was obtained with isofluran 1,5 %, using Midmark MatrXTM VME2® machine.

In swine, in field conditions, azaperone i.m. was used for premedication and ketamine i.v. for induction. In the clinic, atropine s.c. and azaperone i.m. were used for premedication and propofol was used for induction and maintaining the anesthesia, with the FM Braun automatic perfusion device. Sufentanil was administrated for intraoperatory analgesia.


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Clinical monitoring was done using the major semiological methods and by the use of the Midray PM-9000Vet multiparameter, assesing the heart rate, respiratory frequency, respiratory volume, temperature, capilary refill time, presence of the palpebral reflex and movements of the eye, SpO2, arterial blood pressure, measured noninvasively, ETCO2, ECG.

In these species, we’ve chosen the subcutaneous premuscular- aponevrotic tehnique due to the fact that it is easier to apply and more expeditive. We took into account the fact that bovines do not tolerate decubital position for a long time and that in swine, the risc of infection is higher because of the field condition.

The prosthetic mesh is placed superficial, over the hernial rings and then fixated with suture material to the edges, in a vertical pattern (Fig. 7, 8 şi 9), every 2 cm.

Fig. 7. Positioning and suturing of the mesh in bovine

Fig. 8. Positioning and suturing of the mesh in sheep

Fig. 9. Positioning and suturing of the mesh in swine

Postoperative, antibiotics were administered for 3 days, monitoring the general status

(apetite, temperature, heart rate, respiratory frequency, presence/absence of rumination), local healing processes evolution and possible complications (seromas, haematomas, infections, recurrences). The bovine that was also operated for caesarian presented inapetence, thus she was administered Hartman solution and glucosis 5% perfusion, for 3 days postoperative.

Results

Postoperative, the bovine and the sheep had a very good clinical evolution. The bovine

that also had a caesarian presented no rumination for 4 days postoperative and a slight hipertermia, the other physiological functions being in normal ranges. From the point of view of local healing evolution, only in the calf there was seen a seroma, two days after the surgery, that resolved without medication in the next 7 days.

From the three species, the swine presented the best postoperative evolution, after several hours, all the patients had apetite and dinamy. Due to the difficult conditions of field monitoring, in the case of the swine, only the temperature was registered and was in the normal phisiological


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values. The healing of the local process did not present any postoperative complications, in both species, except in the case of the calf.

Considering the good postoperative evolution of the healing of the abdominal wall, in both species, the clinical biocompatibility of the polypropylene meshes was very high.

In the case of great economical valuable pacients or when the economical conditions permit it, the use of polypropylene meshes to remedy the parietal abdominal defects in ruminants and swine, is a modern solution, that prevents losses due to the complications of this pathology.

BIOCOMPATIBILITY OF PROSTHETIC MESHES IN RABBITS

Aim of the study The purpose of the study was the evaluation of two surgical procedures of implantation

of prosthetic polypropylene meshes at the abdominal level in a rabbit model, clinical evaluation of postoperative complications and appreciation of tissue integration - macroscopic and microscopic - induced by prosthetic implants at defined postoperative time intervals - 30, 60 and 90 days.

Observations were conducted in accordance with the Commission of Ethics of the University of Agricultural Sciences and Veterinary Medicine from Cluj-Napoca and were made on a number of 15 domestic rabbits, divided into three groups of 5 rabbits each. The animals weighted between 2000-3000 g and were housed in individual cages, with food and water provided ad libidum. The animals were acclimated 10 days prior to surgery.

Each animal received 150 mg of Cefazolin preoperative. Anesthetic management consisted in administration of a combination of xylazine in dose of 5 mg/kc and ketamine in dose of 50 mg/kc. The anesthetics were administered intramuscularly.

The experimental design consisted in performing of standard abdominal defects, 3x3 cm for each animal from the three groups, placing 4X4 cm polypropylene meshes as substitution of these defects (sublay technique) - the right side- and the implantation meshes of the same dimentions, symmetrically on the left side, in the onlay position. The animals were slaughtered at intervals of 30, 60 and 90 days postoperative and the local behavior of implanted meshes was studied.

Results

There were no intraoperative complications. At 30 days postoperative we observed covering of meshes with a white thin coating of connective tissue, translucent, smooth and easily detachable. After 60 days the mesh was showing a dense scar of fibrous conjunctive, well represented tissue and adherent to both surfaces of the mesh, after 90 days, practically both meshes were found embedded in a fibrous conjunctive tissue, very resistant and hard detachable (Fig. 10).

After all periods of time and in all groups, prosthetic meshes have undergone no structural degradation. Phenomena of neovascularisation (Fig. 11), distributed unequal on the skin surface of the meshes were observed at all three postoperative intervals, but were most obvious in the first 2 intervals.


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Fig. 10. Mesh aspect

(90 days postoperative)

Fig. 11. Neovascularisation

The main postoperative complications that occurred are shown in table 3.

Table 3

Macroscopic local abnormal findings seen after 30, 60 şi 90 days postoperative

Changes Day 30 Day 60 Day 90

Total

Onlay mesh

Sublay mesh

Onlay mesh

Sublay mesh

Onlay mesh

Sublay mesh

Seromas-hematomas

2 1 — — — — 3

Abdominal adherences

— 4 — 5 — 4 13

Suture wires broken

1 — 1 1 1 — 4

Mesh shrinking

— — 1 — 1 — 2

Mesh infection

1 — 2 — 1 — 4

The animal was euthanisied in 16th day postoperative and excluded from the study

Seromas were observed in three animals, in two animals in case of onlay fixated meshes and in one animal in case of sublay fixation. These inflammatory exudative accumulations, consequence of mesh-host tissue contact resolved after rubefactions with iodine tincture every 2 days. In the cases of infected meshes we performed removal of the suture material and application of a topical drug therapy, followed by fixation of sutures.

During healing processes, adherences between meshes and abdominal viscera occurred. We consider these adherences in three major grades:

- grade 0 – discreet adherences - grade 1 – moderate adherences (under 50% of mesh surface with adherences) (Fig. 12). - grad2 2 – severe adherences (above 50% of mesh surface with adherences) (Fig. 13).

Adherences, dense and present both in the center and in the periphery of the meshes, were due to the contact between polypropylene mesh and the abdominal viscera, in our cases viscera involved being epiploon, small bowel and caecum.

Number and type of the adherences after the three postoperative intervals can be seen in graph 1.

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Sublay mesh

60 days postoperative Sublay mesh

90 days postoperative Sublay mesh

30 days postoperative

Graph 1. Number and type of the adherences between prosthetic mesh and abdominal viscera after 30, 60 and 90 days postoperative.

Phenomena of pleating and shrinking mesh were observed in case of mesh implanted

subcutaneous premuscular aponevrosis. (Fig. 14 and 15). Infections of implant locuses were observed in case of onlay fixations Fig. 14), due to superficial placement of the mesh and large spaces generated because of dilacerations.

Fig. 14. Mesh infection and pleating Fig. 15. Suture material ruptured

and mesh pleating After macroscopic examination of the meshes, at the intervals, samples were collected for

histological examination, to observe tissue integration and local behavior of meshes. The biomaterial, abdominal fascia and peritoneum were harvested en bloc from the junction with the host tissue. Samples were fixed with 10% formalin, processed with paraffin, stained with hematoxylin-eosin (H & E) and examined with optical microscope.

It should be noted that during histological processing, especially in the staining phase, prosthetic microfilaments are not kept, are loose, so there remains only the locuses surrounded by specific reactions which will be presented below.

At 30 days, inflammatory cell reaction was more intense in the case of epifascial (onlay) fixation of the meshes. Cell infiltration (esspecially macrophages, few granulocytes and eosinophils) was disposed both peri-and inter-filamentary. Many granulocytes and even multinuclear cells were in necrosis, especially those interfibrillar; some giant cells in necrosis were calcified. Around the meshes, a granulation connective tissue with various degrees of maturation was formed, being well vascularized. Granulation tissue, including microvessels was


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present in mesh stitches, but were not present between the mesh microfilaments; granulomatous reaction was intense.

If sublay fixation cell inflammatory response has been weak, existing multinuclear cells (granulomatous reaction) and mononuclear, but fewer than in onlay fixation. Also fibroplasia was lower.

A particular aspect was the existence of the conjuctive adipose and lax tissue on both sides of the meshes and adjacent fibrosis, suggesting some mobility between the layers of abdominal wall.

After 60 days we observed a decrease in the inflammatory response in both types of fixations, keeping multinuclear cells in low number. In the case of onlay fixation, the sheath of fibrous tissue around the meshes was thiner than that around meshes in sublay fixation.

Moreover, the fibrous tissue around the meshes fixed sublay kept its proliferative phenotype, with persisting fibroblastic cells and an abundant microvascularization. The number of macrophages was reduced in both fixations. The number of multinuclear cells was greater in cases of sublay fixations.

After 90 days we can say that the body has developed a biocompatible chronic foreign body reaction. The reaction of chronic foreign body appears quite discreetly in preperitoneal fixation, due to the existence of giant cells of foreign body, few in number and relatively moderate in size, interposing themselves between mesh microfilaments and proliferated peripheral tissue. The connective tissue, coverring the microfilaments is a relatively dense connective tissue in preperitoneal fixation and well vascularized by the neoformation small vessels. It still has the consolidation inclination, especially in the area immediately adjacent to microfilaments, although, in this case also, it appears to be well consolidated, vascularized, without any pathological aspect.

The intensity of foreign body reaction, granulomatous is low after 90 days in preperitoneal fixation, with very good conditions for the evolution of the final reparatory processes. Even if these processes are not completed after 90 days, they evolve clearly towards a favorable healing with fibrous tissue. Thus, finally, all prosthetic biomaterial appears covered by fibrous connective tissue (relatively thick), reinforcing it, in preperitoneal fixation, strengthening the area. Moreover, this connective tissue is interposed between the biomaterial and muscle fibers, having no influence on the biofunctionality of the abdominal wall.

In epifascial fixation, after 90 days, things are a little different. Granulomatous reaction has a greater intensity, but not beyond certain limits (necrosis, infection). Also, here the locuses of meshes appear surrounded by giant cells, which are significantly in larger numbers and much larger than those present in preperitoneal fixation. We can say that we have, in this case, a lower degree of biocompatibility, mesh creating a greater "morphologically discomfort" than in the case of preperitoneal fixation.

Also in epifascial fixation the body responds by reparatory processes that attempt to cover prosthetic microfilaments in connective tissue, but these processes are in early stages, the area being occupied by lax connective tissue, composed of fine fibers, very young and in some places, with moderate infiltrate with mononuclears (lymphocytes and plasmocytes). There are also vessels of neoformation, but in smaller number, which coexist alongside vessels with relatively dilated lumen in which fibrin networks and other structural changes of the walls can be observed. This shows that these vessels are compromised, vascularization of the area becomes resolved by multiplying the vessels of neoformation. To do that, a certain period of time, difficult to assess at this time, has to pass.

Overall, the reparatory processes appear to evolve favorable also in epifascial fixation, but the time needed to complete this processes is much longer than in the case of preperitoneal fixation.


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Our study observed that placing the mesh in the subcutaneous premuscular aponevrosis or epifascial (onlay) tehnique, anterior to the right abdominal muscle, has the advantage of rapidity and easyness in fixation, and also the fact that it does not come in contact with abdominal viscera. Disadvantages consist in the extensive dilaceration of the connective tissue and the difficulty of suturing above mesh, so, this placement induces more frequent the formation of seromas and infections.

Placing of the mesh in the preperitoneal space or retromuscular (sublay) is more efficient, the mesh being under intra-abdominal pressure, thus standing near the abdominal wall. Fixation provides a higher resistance to abdominal wall pressure, by an increased degree of incorporation into host tissue, lower intensity of foreign body reaction observed at 90 days postoperative and by "dressing" the biomaterial in a fibrous matrix that is well represented. However, it has the disadvantage of being a more difficult procedure.

General conclusions and recommendations The use of some polypropylene prosthetic biomaterials in the remedy of abdominal wall

defects in some species (equine, dogs, bovine, sheep, swine) is a more efficient alternative than the simple raffie of these defects, that insures a good closure, without overtentionning the abdominal wall, decreasing the possible postoperative complications.

To correctly fixate the mesh, an adequate general anesthesia is necessary, with efficiency of both the miorelaxant and analgesic components. We have obtained this principally using inhalatory anesthesia, through specific protocols for each patient.

The premuscular-aponevrotic (epifascial) tehnique is easier to apply and needs less time to apply it, with usage even in field conditions and in farm animals, but it predisposes to seromas, haematomas and infections, due to the mesh positioning and excesive dilacerations. The retromuscular procedure (preperitoneal) is more laboreaous, but insures a better resistence ot the area, the mesh being under the direct pressure of the abdominal viscera.

In case of preperitoneal fixation, to prevent formation of the adherences between mesh and abdomina viscera, omentopexy on the internal surface of the mesh or a thin coating antibiotic at this level is necessary.

Postoperative, the clinical general status was more altered in horses, then in dogs, while ruminants and swine these alterations were very discreate.

Clinicaly, the evolution of the healing processes varried from specie to specie. In swine and ruminants the healing process took place in the shortest period of time, without complications, wilest in horses, it took longer, with inflamatory processes and sometimes other complications.

Monitoring of local healing processes showed appearance of some complications represented by seromas, hematomas and rarely localised infections.

Postoperative recurrence was observed in two patients (a horse and a dog), because of an inadequate postoperative dietary management and a poor resistance of the abdominal wall due to the anterior surgeries.

In horses and dogs, mesh prosthetics determined a sistemic inflamatory process in the first days postoperative, increasing significantly the values of leucocytes, reactive proteine C and fibrinogen, decreasing albumine, though two weeks postoperative the values were in normal ranges.

The postoperative increase of IgE in equine and dogs was not clinically supported (alergic reactions, mesh rejection).

Observaţii privind utilizarea biomaterialelor protetice din polipropilenă în defecte parietale abdominale la animale 2011

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The rabbit experimental study demonstrated that the preperitoneal tehnique ensures a superior mecanical resistence than the epifascial tehnique.

Our experimental and clinical studies offer - clinic and paraclinic – the possibility of observing in dynamic, the local and general phenomena which take place after implant of the prosthetic biomaterials at the abdominal wall level. In consulted literature, a very few dates regarding these aspestc are related.

The results we obtained by testing biocompatibility of the prosthetic biomaterials in defects of the abdominal wall in animals, could be useful like models for testing other biomaterials with utility in plastic and reconstructive surgery of human medicine.

Based on our results in this study, we can recomend the use of polypropylene prosthetic biomaterials in surgical remedy of animal abdominal defects, independent of the defects size.

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CIPRIAN ANDREI OBER - USAMV Cluj · ciprian andrei ober . summary of the phd thesis . observations regarding the usage of the polypropylene prosthetic biomaterials in abdominal wall